Abstract

We used a polyphasic approach combining data from microscopic assessment of fresh biomass and from clone libraries and DGGE fingerprints based on 16S rRNA gene sequences to investigate the cyanobacterial diversity of Czech reservoirs during the summer in 2001 and 2002. A total of 15 genera was identified using the microscopic analysis in 38 samples analysed. They were Anabaena, Anabaenopsis, Aphanizomenon, Aphanocapsa, Aphanothece, Coelomoron, Limnothrix, Merismopedia, Microcystis, Planktolyngbya, Planktothrix, Pseudanabaena, Romeria, Snowella and Woronichinia. We recovered 113 DGGE band sequences from the same samples. In addition, 128 partial 16S rRNA sequences were obtained from two clone libraries of reservoirs Pilská and Orlík. The phylogenetic comparison with the currently available rRNA sequences in databases showed that our sequences belonged to 7 cyanobacterial clusters: Anabaena/Aphanizomenon, Limnothrix, Microcystis, Snowella, Synechococcus, Planktothrix, Woronichinia and a plastid related to Chrysochromulina polylepis (Prymnesiophyceae). Identification of the major populations by the microscopic enumeration and the molecular results were generally congruent (for 32 samples out of 38). Anabaena/Aphanizomenon, Microcystis and Woronichinia were the major genera in the Czech reservoirs during summer, and were present in most of the samples. This study showed some discrepancies between the genera retrieved by the traditional method and the molecular analyses. Differences concerned the presence of minor populations belonging to the genera Aphanothece, Merismopedia, Pseudanabaena, Romeria, Snowella and Synechococcus. These differences can be explained by biases specific to each method (competitive amplification, difficulty to obtain sequences from DGGE bands, problems of microscopic observation of the small-sized genera).